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1. Field of the Invention
The present invention relates to a method of installing a floating marine platform in a deep water environment(over 1500 feet of water). More particularly, the present invention relates to a novel method of installing a marine platform using multiple buoys that support a platform, wherein articulating connections form an interface between the platform and the buoys. In an alternate method, the multiple buoys can be used as part of an installation method to place the marine platform upon a single spar support.
2. General Background of the Invention
Many types of marine platforms have been designed, patented, and/or used commercially. Marine platforms typically take the form of either fixed platforms that include a large underwater support structure or xe2x80x9cjacketxe2x80x9d or a floating platform having a submersible support. Sometimes these platforms are called semi-submersible rigs.
Jack-up barges are another type of platform that can be used in an offshore marine environment for drilling/production. Jack-up barges have a barge with long legs that can be powered up for travel and powered down to elevate the barge above the water.
Other types of platforms for deep water (1500 feet or deeper) have been patented. The September 2000 issue of Offshore Magazine shows many floating offshore platforms for use in deep water drilling and/or production. Some of the following patents relate to offshore platforms, some of which are buoy type offshore platforms, all of which are hereby incorporated herein by reference. Other patents have issued that relate in general to floating structures, and include some patents disclosing structures that would not be suitable for use in oil and gas well drilling and/or production.
One of the problems with single floater type marine platform constructions is that the single floater must be enormous, and thus very expensive to manufacture, transport, and install. In a marine environment, such a structure must support an oil and gas well drilling rig or production platform weighing between 5,000 and 40,000 tons, for example (or even a package of between 500-100,000 tons).
The present invention provides an improved offshore marine platform (and method of installation) that can be used for drilling for oil and/or gas or in the production of oil and gas from an offshore environment. Such drilling and/or production facilities typically weigh between 500-100,000 tons, more commonly between 3,000-50,000 tons.
The apparatus of the present invention thus provides a marine platform that is comprised of a plurality of spaced apart buoys and a superstructure having a periphery that includes a plurality of attachment positions, one attachment position for each buoy. An articulating connection joins each buoy to the platform superstructure.
Each of the buoys will move due to current and/or wind and/or wave action or due to other dynamic marine environmental factors. xe2x80x9cArticulating connectionxe2x80x9d as used herein should be understood to mean any connection or joint that connects a buoy to the superstructure, transmits axial and shear forces, and allows the support buoy(s) to move relative to the superstructure without separation, and wherein the bending moment transferred to the superstructure from one of the so connected buoys or from multiple of the so connected buoys is reduced, minimized or substantially eliminated. xe2x80x9cArticulating connectionxe2x80x9d is a joint movably connecting a buoy to a superstructure wherein axial and tangential forces are substantially transmitted, however, transfer of bending moment is substantially reduced or minimized through the joint allowing relative movement between the buoy and the superstructure.
An articulating connection connects each buoy to the platform at a respective attachment position, the connection allowing for sea state induced buoy motions while minimizing effects on the platform.
The apparatus of the present invention provides a marine platform that further comprises a mooring extending from a plurality of the buoys for holding the platform and buoys to a desired location.
In a preferred embodiment, the present invention provides a marine platform wherein each of the articulating connections includes corresponding concave and convex engaging portions. In another embodiment, a universal type joint is disclosed.
In another embodiment a marine platform has buoys with convex articulating portions and the platform has correspondingly shaped concave articulating portions.
In a preferred embodiment, each buoy can be provided with a concave articulating portion and the platform with a corresponding convex articulating portion that engages a buoy.
In a preferred embodiment, each buoy has a height and a diameter. In a preferred embodiment, the height is much greater than the diameter for each of the buoys.
In the preferred embodiment, each buoy is preferably between about 25 and 100 feet in diameter.
The apparatus of the present invention preferably provides a plurality of buoys, wherein each buoy is between about 100 and 500 feet in height.
The buoys can be of a generally uniform diameter along a majority of the buoy. However, each buoy can have a variable diameter in an alternate embodiment.
In a preferred embodiment, each buoy is generally cylindrically shaped. However, each buoy can be provided with simply an upper end portion that is generally cylindrically shaped.
In a preferred embodiment, there are at least three buoys and at least three attachment positions, preferably four buoys and four attachment positions.
In a preferred embodiment, each articulated connection is preferably hemispherically shaped for the upper end portion of each buoy and there is a correspondingly concavely shaped receptacle on the platform that fits the surface of each hemispherically shaped upper end portion.
In a preferred embodiment, the platform is comprised of a trussed deck. The trussed deck preferably has lower horizontal members, upper horizontal members and a plurality of inclined members spanning between the upper and lower horizontal members, and wherein the attachment positions are next to the lower horizontal member.
In the preferred embodiment, the apparatus supports an oil and gas well drilling and/or production platform weighing between 500 and 100,000 tons, more particularly, weighing between 3,000 tons and 50,000.
The apparatus of the present invention uses articulating connections between the submerged portion of the buoy and the superstructure to minimize or reduce topside, wave induced motions during the structural life of the apparatus.
The apparatus of the present invention thus enables smaller, multiple hull components to be used to support the superstructure than a single column or single buoy floater.
With the present invention, the topside angular motion is reduced and is less than the topside angular motion of a single column floater of comparable weight.
With the present invention, there is substantially no bending moment or minimum bending moment transferred between each buoy and the structure being supported. The present invention thus minimizes or substantially eliminates moment transfer at the articulating connection that is formed between each buoy and the structure being supported. The buoys are thus substantially free to move in any direction relative to the supported structure or load excepting motion that would separate a buoy from the supported structure.
The present invention has particular utility in the supporting of oil and gas well drilling facilities and oil and gas well drilling production facilities. The apparatus of the present invention has particular utility in very deep water, for example, in excess of 1500 feet.
The present invention also has particular utility in tropical environments (for example West Africa and Brazil) wherein the environment produces long period swell action.
The present invention provides a method of installing an oil and gas well facility such as a drilling facility or a production facility on a platform in an offshore deepwater marine environment. The term xe2x80x9cdeepwaterxe2x80x9d as used herein means water depths of in excess of 1500 feet.
The method of the present invention contemplates the placement of a plurality of buoys at a selected offshore location, a portion of each of the buoys being underwater. A superstructure extends above water and includes a platform having an oil and gas well facility. Such a facility can include oil well drilling, oil well production, or a combination of oil well drilling and production. The platform and its facility can be floated to a selected location. The platform includes a peripheral portion having a plurality of attachment positions, one attachment position for each buoy.
When the buoys and platform are located at a desired position, the platform is ballasted relative to the buoys until the buoys connect with the platform. This connection can be achieved by either ballasting the platform downwardly (such as for example, using a ballasted transport barge), or by ballasting the buoys to a higher position so that they engage the supported platform.
In the preferred embodiment, the buoys can be elongated, cylindrically shaped buoys, each having a diameter of for example, 25-100 feet and a height of preferably between about 100 and 500 feet. Each of the buoys can have an upper, smaller diameter portion that includes a connector. In one embodiment, the connector can be convex in shape and articulate with a correspondingly shaped concave connector on the platform.
The platform can include a trussed deck that carries at or near its periphery or corners, connectors that enable a connection to be formed with the upper end portion of each buoy. As an example, there can be provided four buoys and four connectors on the trussed deck or platform.
If a trussed deck is employed, an oil well production facility (drilling or production or a combination) can be supported upon the trussed deck. The connector at the top of each buoy can be any type of an articulating connection that forms an articulation with the trussed deck or a connector on the trussed deck. Examples include the ball and socket or concave/convex arrangement shown in the drawings (FIGS. 1-12). Another example includes the universal joint shown in the drawings (see FIGS. 13-14).
In an alternate method, the multiple buoys can be used as part of an installation method to place the marine platform upon a single spar support.